Numerous items such as smart phones, smart watches, tablets, automobiles, aerial drones, appliances, aircraft, exercise aids, and game controllers may utilize motion sensors during their operation. In many applications, various types of motion sensors such as accelerometers and gyroscopes may be analyzed independently or together in order to determine varied information for particular applications. For example, gyroscopes and accelerometers may be used in gaming applications (e.g., smart phones or game controllers) to capture complex movements by a user, drones and other aircraft may determine orientation based on gyroscope measurements (e.g., roll, pitch, and yaw), and vehicles may utilize measurements for determining direction (e.g., for dead reckoning) and safety (e.g., to recognizing skid or roll-over conditions).
Motion sensors such as accelerometers and gyroscopes may be manufactured as microelectromechanical (MEMS) sensors that are fabricated using semiconductor manufacturing techniques. A MEMS sensor may include movable proof masses that can respond to forces such as linear acceleration (e.g., for MEMS accelerometers), angular velocity (e.g., for MEMS gyroscopes), and magnetic field. The operation of these forces on the movable proof masses may be measured based on the movement of the proof masses in response to the forces. In some implementations, this movement is measured based on distance between the movable proof masses and sense electrodes, which form capacitors for sensing the movement.
A MEMS sensor may be constructed of multiple layers that are bonded together, such as a cap layer, a MEMS layer, and a substrate layer. The movable MEMS components of the MEMS sensor may be located within the MEMS layer and anchored to one or both of the cap layer and the substrate layer. If the location of the MEMS components relative to sense electrodes is different than an expected location, the capacitance that is used to determine the inertial force may be incorrect. Deviation from an expected location of MEMS components may result from a variety of circumstances such as manufacturing tolerances, manufacturing errors, packaging with other components, or stresses experienced during sensor operation.